Speed Pulse wire - connecting new head unit

  1. My model of MX-5 is: __2009 NC2 1.8
  2. I’m based near: __glasgow
  3. I’m looking for technical help or recommendations on: __fitting new head unit

I have the basic 1.8l nc2 with the factory fitted stereo (non Bose). I’ve purchase a new head unit - Kenwood DMX8020DABS - which I planned to fit this weekend.

However, the instructions require me to attach a supplied speed sensor wire in the head unit to the speed pulse unit in the car. I can’t actually work out where this is, and also can’t find anything on how to attach it even if I did find it! Has anyone done this with this model of NC, and who could advise how I should do it?

I can always use a specialist to fit, but would quite like to try it myself.


I remember asking this question a few years ago, I received an answer from someone but don’t ask me what it was.:thinking:
I never investigated further and can’t remember any advice, I too would find it helpful to know if it can be achieved.

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I would imagine this is to provide automatic speed-related volume control.
Hardly essential.

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Well no not essential but handy to have.
You wouldn’t have to keep increasing and reducing the volume manually.:+1:

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Apparently you can’t keep the phone connected to the unit wirelessly unless the speed pulse wire is also connected. Not immediately obvious why, but it makes it a pretty important connection.

Can’t help on that one, sorry.

I can’t believe that speed pulse wire will affect the wireless connection, I’m no expert, I suppose suck it and see.:thinking:

On my last head unit install there was no mention this wire being available, can’t even remember one coming from the JVC head unit.
Back around 6 years ago I had such a wire from the rear of a Sony head unit but no where for it to connect to.

It’s all a bit too much of a bother to get an expert to take a look, for me anyways but i agree if you can find a solution whilst your about this job then👍

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Hmm, have a look at the White wire pin 1I (1i) on the Mazda loom connector for the head unit (audio system). It MIGHT be the one you need.

That wire carries an output from pin 2O (not twenty) on the Instrument Cluster, where the tacho lives. It will expect an input pull-up load resistor within the audio system. This is a Non-Bose connection. (Bose uses its microphone to compensate for cabin noise.)

Click on the arrow on manual page 0920-2 for the circuit diagram showing the head unit end, pin 1I

and again on manual page 0922-1a for the cluster end, pin 2O

Note this is USA wiring, so the colours might vary, but the pinouts should be the same.

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I’ve booked it in for a professional install on Monday. Too many chances for me to get things wrong, so best left to someone who knows what he’s doing!

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New head unit now fitted, and all seems to be working well. Quite a lot of glare with the top down - makes the satnav tricky to read, so will need to experiment with the display settings

Any joy with the speed sensor wire?

Left it to the installer to sort out, and forgot to ask where it was. Everything works, so they must have found it.

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